Bottle

There are three things that requires obtaining a bottle in a normal run.

1. You need Ruto's Letter bottle to get past King Zora.
2. You need to put a fish in a bottle and bring it to Lord Jabu Jabu to get inside his belly.
3. You need one to obtain blue fire to get past Red Ice Walls and Blocks in Zora's Domain, the Ice Cavern, and Ganon's Castle Trials.

To get past the first two obstacles, check out how to skip King Zora and enter Jabu Jabu without a Fish. All that remains is getting around all that Red Ice.

Getting into Ice Cavern's left wing

Discovered by ZFG

In the room with the spinning ice scythe there is a red ice wall to the left. At the very edge of the left side of the ice wall you have a few options, you can either perform a very precise Superslide to clip through it, or use a Recoil Hoverboost to get through.

Ice Cavern Silver Rupee inside the Red Ice

Discovered by Kazooie

In the ice block puzzle room you need to collect 5 silver rupees to open bars leading to the last room. There is a rupee encased in red ice. Simply jumpslash at the red ice at the right angle and you will get the rupee.

Last Red Ice Blocks before Iron Boots

There are 3 Red Ice Blocks before the door to the Iron Boots room. Simply Superslide or Megaflip into it to get past it.

Pass the Red Ice in Ganons Castle Water Trial

Discovered by MrGrunz (1st wall), ZeldaXMaster (?) (2nd wall)

For the first wall, kill a freezzard then lure the other freezzard next to the red ice wall. Take out the hookshot, go up against the ice wall, press Z to go into 3rd person and use the freezzard to hookshot clip into the ice wall. Then just kill the freezzard to unlock the door.

For the wall in the 2nd room, you can just jumpslash at the switch with the hammer in order to skip melting the red ice.